Many document copying machines require that a document be held in a stationary manner face down on a document glass in order to be copied. Frequently, in a copier of this type, it is necessary for the operator to place the document on the document glass manually. However, in some machines, the operator may feed documents onto the document glass by inserting them one at a time into an automatic feeding arrangement. Mechanisms of this type are known as semiautomatic document feeds (SADF). In other machines, the operator may place a stack of documents upon a feed tray from which they are automatically fed. Mechanisms of this second type are known as automatic document feeds (ADF).
Whether a semiautomatic document feed or an automatic document feed is utilized, it is necessary for some mechanisms to move the paper across the document glass and register it accurately thereon for the copying operation. A common type of paper forwarding device is a belt located above the document glass such as described in U.S. Patent Application, Ser. No. 926,979, now U.S. Pat. No. 4,203,585. While belt mechanisms of this type are in general use, they are difficult to adjust so as to provide accurate registration of documents and without accurate registration, information can be lost during the copying process. It has been found that when compliant rollers are used instead of belts as the paper forwarding mechanism, this problem is greatly reduced.
When compliant rollers such as rollers made from foraminous material are used as the document advancing mechanism in a document feed, a problem is presented in that the rollers must be precisely located in the vertical dimension relative to the horizontal document glass in order to perform the operation successfully. In order to obtain precise mounting, the roller drive shafts and bearing blocks must be solidly mounted on a platen cover at a precise distance above the glass. However, when rigid elements of this kind are interposed above the glass, further problems develop such as cracking of the glass when stray objects, such as pens, are inadvertently left on the glass when the rigid cover is closed. Also, since the typical document glass cover is hinged to pivot between open and closed positions, and may be subject to rough use by a variety of operators, the pivoting action of the cover can create accumulative stresses on the frame so that preciseness in mounting the rollers is lost after a period of use. This invention provides an answer to these problems.
When using a series of rollers to move paper across the document glass, complex drive problems result which may be accentuated by the need to position rollers at an angle to the drive direction in order to move the paper into a reference edge for proper positioning. This problem becomes even more severe when two documents are fed simultaneously onto the document glass with one document being positioned along a front reference edge and the second document positioned along a rear reference edge so that the two documents can be copied simultaneously such as described in U.S. Pat. No. 4,052,054. This problem is made more severe when large documents are to be copied and come under the influence of some rollers tending to position it along the front reference edge and others tending to position it along the rear reference edge. This invention not only provides a simple drive for a series of rollers, it meets these positioning problems as well.
In the machine described in the aforementioned U.S. Patent Application, now allowed, the paper is registered against a positioning gate. At the conclusion of a copying process, when the gate is withdrawn so that the paper may be automatically expelled from the document glass, there is a tendency for paper to catch in the fingers of the gate as they retract; this is especially true of very lightweight paper. It is therefore, an object of this invention to position paper so as to prevent jams in the positioning gate.